I did a little acoustic test. Tapped on the P3 with a metal ruler. The back panel is obviously aluminum and gives a metal on metal tick when tapped. So does the side up to the seam. Tap on the top piece and the sound changes to a more dampened sound. Same sound as when I tap the ruler on my plastic keyboard body. You can also tell plastic from glass faces by the difference in sounds when tapped.

I did a little acoustic test. Tapped on the P3 with a metal ruler. The back panel is obviously aluminum and gives a metal on metal tick when tapped. So does the side up to the seam. Tap on the top piece and the sound changes to a more dampened sound. Same sound as when I tap the ruler on my plastic keyboard body. You can also tell plastic from glass faces by the difference in sounds when tapped.